455 is one of the easiest/reliable starting saws I've ever seen. Like has been said, the saw cannot be flooded with the primer bulb.
Question 1: How many times does he pull the rope with the choke on? Over-choking is the most common way to flood a saw. I'm guessing he's missing the initial "pop" and continuing to pull with the choke on. This is pretty common.
Question 2: Was this saw set up and adjusted at time of purchase? Too lean on the lo adjustment makes for a harder starting saw. Another indication here would be real boggy acceleration on start up unti, warm.
Question 3: Does the primer bulb firm up/fill up after 3-4 pumps? If it stays empty the carb is probably junk. But this issue is generally found on a saw that constantly stalls, so if the saw runs OK once started, then don;t worry about this one.